(1) Field of the Invention
This invention relates to attenuating phase shifting masks and more particularly to the location and formation of sub-resolution contact holes around test patterns formed in the frame cell region of the mask border.
(2) Description of the Related Art
TSMC-96-293, Ser. No. 08/857,166 now U.S. Pat. No. 5,817,439, Filed May 15, 1997, entitled "A NEW METHOD OF BLIND BORDER PATTERN LAYOUT FOR ATTENUATED PHASE SHIFTING MASKS", and assigned to the same assignee describes a method of locating sub-resolution contact holes in the border region of attenuating phase shifting masks.
"ULSI Technology", by C. M. Chang and S. M. Sze, McGraw-Hill Companies, 1996, pages 284-289 describes a method of forming an attenuating phase shifting mask.
U.S. Pat. No. 5,446,521 to Hainsey et al. describes an attenuating phase shifting mask using a sub-resolution pattern of lines and spaces in the scribeline part of the mask pattern.
U.S. Pat. No. 5,565,286 to Lin describes a structure and fabrication method for a phase shifting mask using an attenuating phase shifting mask structure combined with an alternating element phase shifting structure.
U.S. Pat. No. 5,620,816 to Dao describes method of mask layout wherein device features are placed on lines and/or columns. The lines and/or columns are extracted from a database.
U.S. Pat. No. 5,644,381 to Miyazaki et al. describes a method of exposing a wafer using an attenuating phase shifting mask. An optimum focal position is determined so that a resist film having a step on its surface can be exposed with high precision.
U.S. Pat. No. 5,537,648 to Liebmann et al. describes a method for automatically generating phase shifted mask designs implemented in a CAD program.
This invention describes a mask and method of mask layout for automatically forming a test pattern in a frame cell region of an attenuating phase shifting mask. The mask incorporates a buffer distance between the test pattern features and sub-resolution contact holes used to prevent side lobe effects in the regions between device regions of the mask. By using the proper buffer distance problems due to side lobe effect at the frame cell region of the mask, where the test pattern is located, are prevented.